Central Military Hospital in Ruzomberok, Gynecological and Obstetrical Department, Zarevuca 3, 03401, Ruzomberok, Slovak Republic

Synonyms: Metatropic dwarfism, Chondrodystrophy - hyperplastic form, Metatropic dwarfism syndrome.

Definition: Metatropic dysplasia is a short limb skeletal dysplasia characterized by dumbbell-like configuration of the long bones, a narrow but normal length thorax, and, occasionally, a coccygeal appendage similar to a tail (Romero)⁶. Sillence D. et al. (2004)⁷ defines metatropic dysplasia (metatropic-changing, hypertrophic achondroplasia) as a severe spondyloepimetaphyseal dysplasia with characteristic clinical and diagnostic radiographic findings. In the newborns and infants:

• there is a long trunk with disproportionately short extremities,
• length is usually normal,
• the chest is narrow
• often there is a 1-3 cm long tail-like appendage at the level of coccyx,
• the joints are prominent with decreased mobility,
• fingers and toes are long,
• the face is uncharacteristic although a prominent forehead and flattened nasal bridge may be present in infancy.

The proportions change during childhood with relative shortening of the trunk due to progressive kyphosis and relatively long extremities. Chest deformity and flexion contractures are associated findings. Hyperextensibility of the fingers may be present. The adult height is up to 120 cm. Intellectual development is normal.

Case report: Prenatal diagnosis of this condition have not been reported, so instead following are the pictures of children suffered from metatropic dysplasia that are available on the internet (see Fig.1).

Fig.1 a) Photograph showing the tail like appendage and kyphoscoliosis in a child suffered from metatropic dysplasia , b) A child with metatropic dysplasia  – notice relatively long trunk and shortened extremities

Prevalence: Metatropic dysplasia is a rare condition whose exact incidence is not known.

Etiology: Some familial cases have been reported, suggesting an autosomal recessive pattern of inheritance. However, most cases occur sporadically (Romero et al.)⁶. Other authors conclude that metatropic dysplasia comprises at least three genetic entities:

1. a nonlethal type with autosomal recessive transmission; 
2. a nonlethal dominant type and 
3. a lethal type with death before or shortly after birth and possibly autosomal recessive inheritance (Beck M. et al, 1983)¹

Pathogenesis: Pathogenesis still remains poorly understood from the morphological and molecular perspectives (Hall C. M, Elcioglu N. H, 2004)²

Sonographic findings: Although prenatal diagnosis of this condition has not been reported, primary features are
• micromelia with marked metaphyseal flaring,
• narrow but relatively long trunk,
• progressive kyphoskoliosis (Nyberg at al., 2003)⁵.
Other possible findings are:
• wide metaphyses (trumpeted shaped widening of the metaphyses, dumbbell configuration),
• shortening of the limbs,
• platyspondyly,
• caudal appendage (tail-like skin fold overlying the sacrum),
• camptodactyly (hammer toes),
• hypoplastic ilia,
• joint contractures (including arthrogryposis),
• long toes,
• short ribs and
• cleft palate (McKusic)⁴.

Differential diagnosis: Others conditions associated with dumbbell configuration of long bones should be considered like:
• Weisenbacher Zweymuller syndrome (severe micromelia, micrognathia, and coronal cleft in the vertebrae),
• Fibrochondrogenesis (rhisomelic limb shortening, broad dumbbell-shaped metaphyses, pear-shaped vertebral bodies, short and distally cupped ribs),
• Kniest syndrome (platyspondyly and coronal cleft, shortened tubular bones and metaphyseal flaring, broad and short thorax) and 
• Dyssegmental dysplasia (micromelia with metaphyseal flaring associated with a cephalocele and abnormal spine).

Associated anomalies: Cleft-palate has been reported in association with metatropic dysplasia (Romero et al., 2002)⁶.

Prognosis: Some patients die during infancy but this condition is compatible with life although with age is increasing disability because of progressive kyphoscoliosis (Romero et al., 2002)⁶.

Management: If the diagnosis is made before viability, the option of pregnancy termination should be offered to the parents. Diagnosis after viability does not change standard obstetrical management (Romero et al., 2002)⁶.

References:

1. Beck M, Roubicek M, Rogers JG, Naumoff P, Spranger J.: Heterogeneity of metatropic dysplasia. Europ. J. Pediat. 140: 231-237, 1983. PubMed ID : 6628444
2. Hall C. M, Elcioglu N. H. Metatropic dysplasia lethal variants. Pediatr Radiol. 2004 Jan;34(1):66-74. Epub 2003 Oct 18. Pub Med ID: 14566438
3. Maroteaux P, Spranger J, Wiedemann HR: Metatropische Zwergwuchs. Arch Kinderheil 173:211, 1966.
4. McKusik. Features listed for metatropic dysplasia. [online]. [quoted 30.01.2005]. Available at: http://www.hgmp.mrc.ac.uk/dhmhd-bin/hum-look-up?1121 
5. Nyberg D. A., McGahan P. J., Pretorius D. H., Pilu G. Diagnostic imagining of fetal anomalies. Philadelphia: Lippincot Williams & Wilkins, 2003. 1002 p. ISBN 0-7817-3211-5
6. Romero R., Pilu G., Jeanty P., Ghidini, Hobbins. Skeletal Dysplasias. [online], [quoted 27.01.2005]. Available at: http://www.sonoworld.com/Client/Fetus/Files/pcda/PDCA_skel.pdf 
7. Sillence D., Kozlowski K. Metatropic Dysplasia. Orphanet encyclopedia, November 2004. Available at: http://www.orpha.net/data/patho/GB/uk-MetatropicDysplasia.pdf